An osteotomy is a surgical procedure involving dividing or cutting a piece out of a bone to correct a bone or joint deformity. Such deformities may result from age, injury, birth defect and/or disease, such as arthritis. A particularly common deformity susceptible to treatment by osteotomy is a varus or valgus displacement of the knee joint, more commonly referred to as a knock-kneed or bow-legged condition, respectively. This condition can be corrected by a tibial osteotomy procedure. A second common type of deformity, frequently caused by overly tight shoes, involves a twisting in of the big toe toward the rest of the foot, known as a hallux valgus deformation. A hallux valgus deformity can frequently be successfully treated by a metatarsal osteotomy to realign the metatarsal.
Angular deformations, such as described above, can be corrected by one of two major osteotomy techniques. In the first of the techniques, the angular alignment of a bone is altered by making a cylindrical profile cut through the bone where the realignment is to be effected. The severed sections of a bone cut in this fashion can be pivoted relative to one another about the axis of the cylindrical cut, while maintaining substantially complete bone contact at the cut. The surgeon must position the bone sections in the desired alignment and stabilize the bone while it heals. Both the stabilization and the alignment can be problematic when this method is employed.
A second technique for correcting angular deformations involves the removal of a cuneiform or wedge-shaped section of bone extending substantially, but not completely, across the bone generally transverse to its long axis. By leaving a small amount of bone at the apex of the wedge, a hinge-like articulation is created, which stabilizes the bone as the gap, which results when the wedge is removed, is closed. By precisely controlling the wedge angle, the desired angular correction is reliably established. In the prior art, the desired angular correction is typically determined pre-operatively by measurements from X-rays of other imaging techniques, and in some cases, by simple visual estimation. The predetermined correction angle is used to set the guide, which is then used to make the cuts.
Several varieties of osteotomy guides for making cuneiform osteotomies are shown in the prior art. U.S. Pat. Nos. 4,627,425 and 4,750,481 to Reese disclose a system to make a second cut at a predetermined angle relative to a first cut. The system employs a flat follower pivotally connected to a saw guide. After making the first cut, the follower is set and secured at the desired predetermined angle relative to the guide and inserted into the first cut. By placing the follower in the first cut, the guide is automatically placed so that the second cut occurs at the desired predetermined angle relative to the first cut.
Numerous references, such as U.S. Pat. Nos. 4,349,018, 4,421,112, 4,565,191, 5,112,334 and 5,246,444, disclose devices that provide two angularly displaced guides, one for each cut, along which both cuts are made without repositioning the device. As with the guide and follower systems described above, such devices require that the surgeon predetermine the desired correction angle.
Either of the above described mechanisms for guiding the cuts at predetermined angles are generally able to accurately establish the cut locations once the wedge angle is set. The primary source of error in such systems thus becomes determining the angle at which to set the devices. Measurements from X-rays of the affected bone or bones are probably the most common method of determining the correction angle. Unfortunately, determining the correct angle from an X-ray is dependent on taking the X-ray from the proper angle relative to the bone or bones. Thus, in the case of the tibial osteotomy, if the patients leg is rotated slightly about its longitudinal axis, i.e., the foot turned in or out, the apparent angle between the tibia and femur may be altered. It is likewise apparent that visual estimation of the correction angle is subject to considerable error.
It is therefore an object of the present invention to provide an osteotomy guide with which it is not necessary to determine preoperatively the desired correction angle.
It is another object of the current invention to provide an osteotomy method in which the correction is automatically established during the osteotomy.
Yet another object of the current invention is to provide an osteotomy method in which the correction angle is determined during the surgery by reference to anatomical landmarks.
One more object of the present invention is to provide an osteotomy guide with a structure suitable for use in determining the correction angle for an osteotomy.
Another object of the present invention is to provide a simple, easy to use osteotomy guide and surgical technique that together result in a rapid and precise osteotomy.